Fuel cells have been proposed as a power source for electric vehicles and other applications. In proton exchange membrane (PEM) type fuel cells, hydrogen is supplied as a fuel to an anode of the fuel cell and oxygen is supplied as an oxidant to a cathode of the fuel cell. A plurality of fuel cells is stacked together in a fuel cell stack to form a fuel cell system. The fuel and oxidant are typically stored in pressurized hollow vessels such as fuel tanks, for example, disposed on an undercarriage of the vehicle.
A typical pressurized vessel 10 is illustrated in FIGS. 1a, 1b, and 2. The vessel 10 includes three shells: an inner shell 12, an intermediate shell 14 formed over the inner shell 12, and an outer shell 16 formed over the intermediate shell 14. The inner shell 12 is typically formed from a polymeric material such as polyethylene, PET, ethylene vinyl alcohol, or an ethylene vinyl acetate terpolymer. The inner shell 12 may also be formed from any moldable material such as a metal, a glass, and the like. The intermediate shell 14 is typically formed by a filament winding process from one of a carbon fiber and a carbon fiber composite and provides structural strength to the vessel 10. The outer shell 16 is typically formed from a glass fiber wound around the intermediate shell 14. The outer shell 16 is typically impregnated with an epoxy or other suitable adhesive to facilitate adhesion of the outer shell 16 with the intermediate shell 14.
The inner shell 12 of the vessel 10 is typically formed over an exterior portion of, or on an interior portion of, a finish facilitating fluid communication with an interior of the vessel 10. In FIG. 1a, the finish is a metallic boss 18. The metallic boss 18 is in communication with a valve 20, but the metallic boss 18 may be in communication with any means for fluid communication (not shown) with other vessel fittings such as a pressure relief device, a nozzle, a conduit, and the like.
To minimize the effects of thermal energy on the inner shell(s) of typical vessels, a metal shell is formed around the outer shell of the vessel. Formation of such metal shells is labor intensive, increases weight, and maximizes both the assembly and material costs of the vessels.
It would be desirable to develop a hollow pressure vessel adapted to minimize the effect of thermal energy on the vessel, while also minimizing the assembly and material costs thereof.